Circuit arrangement for telephonic communication



Oct. 1, .1929.

w. S-CHAFFER CIRCUIT ARRANGEMENT FOR TELEPHONIC COMMUNICATION Filed Aug. 18. 1922 ill" @uoewco'a WALTER SCHAFFER 851 his 61am Patented Get. 1, 1929 sun STTEES WALTER SCHAFFER, OF BERLIN, GERIVIAIQ'Y, 'ASSIGIIOPU T0 GESELLSCHAFT DRAIIT- LOSE TELEGRAPHIE 1H. B. 1-1. HALLESCHES, OF BERLIN, GERIEANY, A CORPOIRATIGN OE GERMANY CIRCUIT ARRANGEMENT FOR TELEPHONIC COMMUNICATION Application filed August 18, 1922, Serial No. 582,610, and in Germany August 31, 1921.

Telephone circuits are known in which the grid of the sending tube 1S connected with the secondary winding of the audio transformer.

These circuits operate in such a manner that in the speech rhythm, positive or negative speech tension is supplied to the grid. In sending tubes of the usual type. the application of speech tension to the grid often causes a breakdown of the oscillations and as a result of this, a distortion of the speech. In accordance with the present invention, no tension is applied to the grid for the purpose of speech but the grid circuitcomprises a variable resistance, preferably in the form of a cathode tube, the resistance value of whichis varied during the speech rhythm by the actuation of its grid.

The single figure of the drawing is a diagrammatic representation of an exemplification of the invention.

In the illustrated circuit arrangement the oscillator tube is denoted by reference character 1. The oscillator tube comprises an anode, a cathode and grid or control electrode. The anode current is supplied by a source of electrical energy 5. Connected across the anode and cathode is a circuit comprising a blocking condenser 20, an in ductance 3 and a second condenser 2.

The antenna circuit 4 is connected to the upper terminal of inductance 3 and the lower terminal of condenser 2 is grounded. The condenser 2 is shunted by a resistance 21 to allow the passage of the control electrode leakage current from tube 1.

The grid circuit is connected across the condenser 2 and comprises a variable resistance in the form of a three electrode vacuum tube 6 similar to the first tube 1. The cathode of modulator tube 6 is connected to the control electrode of the oscillator tube and the anode of modulator tube 6 is connected to the condenser 2. Preferably the tube 6 is connected in series with choke coils 7 and 8 in order to prevent the passage of high frequnecy alternating currents through the tube 6. The circuit including the tube 6 and the choke coils 7 and 8 is connected in parallel with denser 9 through which the high frequency currents may pass. If the resistance of tube 6 is infinitely high, the tube 1 cannot produce oscillations because its grid cannot discharge. The oscillations produced by tube 1 are modified according to the value of the resistance of tube 6. The resistance of tube 6 is varied by actuating its grid by means of the transformer 10, the transmitter 11 and the transmitter battery 12. Experiments have shown that by using a variable resistance in the grid circuit, the oscillations produced by tube 1 are continuously varied and never break down. Instead of directly ctuating the grid of the tube 6 by means of the telephone circuit and the transformer 10, the grid may also be actuated by the received currents in any other well known manner. Thus the arrangement may be used as a receiving amplifier or as a relay sender. Preferably, a high ohmic resistance 13 is connected in parallel with the condenser 9. The purpose of this resistance is to prevent excessively high charging of the grid of tube 1 at times Whenthe tube 6 presents an infinitely high resistance. If the grid of tube '1 were to be come too highly charged, it might cause a break-down from the grid to the cathode of tube land, in certain circumstances, also a break-down in the rhythmic succession.

Having described my invention, what I claim is:

1. In combination, a first electron discharge tube having a cathode, anode and control electrode, means for operating said tube at high frequencies, a second tube similar to said first tube, a connection including a condenser between the anode of the second tube and the cathode of said first tube, a second connection including a choke coil between the cathode of said second tube and the control electrode of said first tube, and means for varying the resistance of said second tube.

2. In combination, a first electron discharge tube having a cathode, anode and control electrode, means for operating said tube at high frequencies, means including a condenser in the control electrode circuit to cause said electrode to accumulate a negative charge, a path between said electrode and the cathode of the first electron dischargetube,

for discharging said charge, said path com prising the anode-cathode circuit of a second tube similar to said first tube and a resistance connected in parallel, and means for varying the resistance of said second tube in accordance with a desired signal.

3. In combination, a first electron discharge tube having a cathode, anode and control electrode, means for operating said tube at high frequencies, means including a condenser for causing said control electrode to accumulate a negative charge, a second tube similar to said first tube, means whereby said second tube is included in the control electrode discharge path, means for varying the resistance of said second tube in accordance with a desired signal and means comprising a resistance in parallel with said sec- 0nd tube whereby the resistance of said discharge path can never exceed a certain amount, a choke coil in series with said sec- 0nd tube and a condenser in parallel with said second tube to protect said second tube against high frequency oscillations.

4. In combination, an electron discharge tube having a cathode, anode and control electrode, an anode supply circuit, an anodecathode circuit including a blocking con denser, an inductance and second condenser in series, a resistance across said second condenser, and a control electrode-cathode circuit across said second condenser, said last named circuit comprising a plurality of parallel circuits.

5. In combination a first electron discharge tube having a cathode, anode and control electrode, an anode supply circuit, an anodecathode circuit including a blocking condenser, an inductance and a second condenser in series, a resistance across said second condenser, a control electrode cathode circuit across said second condenser, said last named circuit including a third condenser and a tube similar to the'first in parallel therewith and means for controlling the resistance of said second tube in accordance with a desired signal.

6. In a transmitting device an electron discharge tube having a cathode, an anode and a control electrode, a resistance circuit for controlling said control electrode comprising a fixed resistance and a variable resistance in parallel, means for varying said variable resistance in accordance with signals to be transmitted and means controlled by said first named resistance whereby a maximum value of said resistance circuit may be predetermined.

WVALTER SCHAFFER. 

